JPH07161288A - Photoelectron emitting surface and electronic tube using it - Google Patents

Abstract

PURPOSE:To reduce a dark current due to applying bias voltage by providing an i-type intermediate layer of high resistance between a light absorbing layer and electron emitting layer of a photoelectron emitting surface, so that a photoelectron can be emitted by the low bias voltage. CONSTITUTION:When near infrared light hnu is incident from an exposed surface of a p<+> type InP semiconductor substrate 1 upon a photoelectron emitting surface applied with suitable bias voltage, the near infrared light hnu, permeating the substrate 1, is absorbed by a p<->InGaAsP light absorbing layer 2, to excite a photoelectron (e). The photoelectron (e) is accelerated by an electric field formed by applying bias voltage, to traverse an interface of the light absorbing layer 2, i-type InP intermediate layer 3 of high resistance and a p<->InP electron emitting layer 4, and after transition to a conduction band, the photoelectron leads to a surface of the electron emitting surface 4. The photoelectron (e) passes through the interface of the light absorbing layer 2 and the intermediate layer 3 by a tunnel effect even at low bias voltage. By applying suitable Cs to a surface of the electron emitting layer 4, the arriving photoelectron (e) is easily emitted to the outside from an exposed surface of the layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectron emitting surface which emits photoelectrons upon incidence of light and an electron tube using the photoelectron emitting surface.

[0002]

2. Description of the Related Art Conventionally, a bias voltage is applied to a hetero-stacked structure of a p-type III-V group compound semiconductor, and an internal electric field causes photoelectrons to transition from the valleys of the conduction band to the valleys L and then to be emitted into a vacuum. The so-called transition electron type photoelectron emission surface is U
S. PAT. 3,958,143.

This is because, for example, a p ⁺ InP substrate 1, a p ^-- InGaAsP light absorption layer 2, a p ^-- InP electron emission layer 4, and a Ag layer having a thickness of 100 Å or less, as shown in the schematic sectional view of FIG.
A structure composed of the thin film Schottky electrode 5 is well known.

FIG. 1 is an energy band diagram when no bias voltage is applied to the transition electron type photoelectron emission surface.
It shows in 0. In this case, the photoelectrons e excited in the conduction band in the p ⁻ InGaAsP light absorption layer 2 cannot reach the surface of the p ⁻ InP electron emission layer 4 due to the energy barrier in the conduction band.

Next, FIG. 11 shows an energy band diagram in the case where an appropriate bias voltage is applied and an internal electric field is formed on the photoelectron emitting surface. In this case, as shown in the figure, the p ^-- InGaAsP light absorption layer 2 and the p ^-- In
The conduction band discontinuity ΔE between the P electron emission layers 4 becomes small. Therefore, the photoelectrons e excited in the conduction band in the p ⁻ InGaAsP light absorption layer 2 can move to the p ⁻ InP electron emission layer 4, and are accelerated by the electric field formed inside the semiconductor, and from the valley of the conduction band. After transitioning to the L valley, it is released to the outside.

However, such a transition electron type photoemission surface of a structure essentially p ^- InGaAsP light absorbing layer 2 and p ^- energy barrier △ E of the conduction band at the interface of InP electron emitting layer 4 is present and Since the width d is such that photoelectrons cannot pass through the tunnel effect, p ^-- In
The photoelectrons e excited in the GaAsP light absorption layer 2 need to be accelerated by an electric field enough to overcome the discontinuity of the conduction band.

In the transition electron type photoelectron emission surface of this structure,
Photoelectron e overcomes this discontinuity in the conduction band and p ^- InP
A certain high bias voltage is required to move to the electron emission layer 4, and the increase in dark current due to the leakage current of holes from the Schottky electrode 5 due to this high bias voltage has been a serious problem.

On the other hand, in order to reduce the dark current, a photoelectron that forms an additional layer of a thin film capable of forming a potential barrier of the highest possible limit inside the valence band while maintaining electron transparency in the light absorption layer. The emission surface is Japanese Patent Publication Sho 62-1
33633. FIG. 12 shows the structure of this photoelectron emitting surface and the energy band diagram when the bias voltage is applied.

The photoelectron emission surface is transparent to the photoelectrons e excited by the incident light and serves as a barrier to the holes h injected from the electrode 19, and the photoabsorption layers 16 and 18. A thin film having a larger energy gap and an appropriate film thickness as the additional layer 17 is used as the light absorption layers 16 and 1
By inserting the holes 8 into electrons, electrons generated by collisional ionization due to acceleration of holes h are suppressed and the dark current is reduced.

[0010]

However, this photoelectron emission surface has a new electric field that allows the photoelectrons e to pass through the conduction band barrier formed by inserting the additional layer 17 into the photoabsorption layers 16 and 18. Therefore, it is necessary to increase the bias voltage. The photoelectron emission surface of FIG. 12 essentially has a defect that the holes h injected from the electrode 19 increase due to the increase of the bias voltage, which is contrary to the original purpose.

The present invention has been made in order to provide a photoelectron emitting surface which does not have the above-mentioned drawbacks, and provides a photoelectron emitting surface capable of emitting electrons at a bias voltage lower than that of the conventional one, and from the photoelectron emitting surface. It is an object of the present invention to provide a high-sensitivity and low-noise electron tube in which the dark current is significantly reduced.

[0012]

In order to achieve the above object, the photoelectron emission surface of the present invention has a hetero-laminated structure of III-V group compound semiconductors and absorbs incident light to excite photoelectrons. The photoelectron emission surface is (a) a light absorption layer having a small energy gap formed on the substrate, and (b) is laminated on the upper surface of the light absorption layer, has a larger energy gap than the light absorption layer, and has a high resistance. An i-type intermediate layer, (c) an electron emission layer stacked on the upper surface of the i-type intermediate layer, (d) a first electrode in contact with the substrate, and (e) a second electrode in contact with the electron emission layer. It is characterized in that incident light is incident from the substrate side and photoelectrons are emitted to the electron emission layer side.

Here, the electron emission layer may be an n-type layer having a thickness of 100 Å or less.

The first electrode in contact with the substrate is formed in a pattern in which at least a part of the substrate surface is exposed, and the second electrode in contact with the electron emission layer is in a pattern in which at least a part of the electron emission layer surface is exposed. Once formed, incident light may be incident from the exposed surface of the substrate and photoelectrons may be emitted from the exposed surface of the electron emitting layer.

The second electrode in contact with the electron emission layer is
It may be made of a metal of Al, Au, Ag, Mo, Ni or W or a silicide or an alloy thereof.

In order to achieve the above object, the electron tube of the present invention is characterized by including the above-mentioned photoelectron emitting surface.

[0017]

When light is incident on the photoelectron emission surface of the present invention from the substrate side with a bias voltage applied in the direction of accelerating photoelectrons via the first and second electrodes, the incident light passes through the substrate. , Is absorbed in the light absorption layer and excites photoelectrons.

On the other hand, when a bias voltage is applied, an internal electric field is formed on the photoelectron emission surface, and band bending occurs due to depletion near the surface, but energy is generated at the interface between the light absorption layer in the conduction band and the i-type intermediate layer. Barriers exist.

The excited photoelectrons are accelerated by an electric field formed by applying a bias voltage, and the photoelectrons and i
Reach the interface of the mold interlayer. Since the energy barrier existing at this interface has a narrower width than that of the conventional one due to the strong internal electric field of the i-type intermediate layer, photoelectrons easily pass through this barrier by the tunnel effect.

The photoelectrons that have passed through the interface between the light absorbing layer and the i-type intermediate layer cross the interface between the i-type intermediate layer and the electron-emitting layer, transition from the bottom of the Γ valley of the conduction band to the bottom of the L valley, and then the electrons. It easily reaches the surface of the release layer and is released to the outside.

Since the photoelectrons e easily pass through the energy barrier of the conduction band due to the tunnel effect, the photoelectrons are emitted by applying a bias voltage much lower than the conventional one. Then, when the bias voltage is lowered, injection of holes into the photoelectron emission surface due to application of the bias voltage is suppressed, and the dark current due to the holes is significantly reduced.

Among the photoelectron emitting surfaces according to the present invention,
In the case of using the ultrathin n-type semiconductor layer as the electron emission layer, since the internal electric field strength of the electron emission layer is low, injection of holes from the electrode in contact with the electron emission layer is further suppressed, and the dark current is further reduced.

Further, the electron tube having the above-mentioned photoelectron emitting surface operates while the dark current is greatly reduced as compared with the conventional one.

[0024]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

A cross-sectional schematic view of an embodiment of the photoelectron emitting surface according to the present invention is shown in FIG. This photoelectron emission surface is p ⁺ type In
P ⁻ InGaAsP light absorption layer 2 on P semiconductor substrate 1
However, a high-resistance i-type InP intermediate layer 3 was epitaxially grown thereon, and a p ^-- InP electron emission layer 4 was epitaxially grown thereon. II
It has an I-V group compound semiconductor hetero-stacked structure. Further, on the electron emission layer 4, an Al Schottky electrode 5 formed in a pattern in which a part of the surface of the electron emission layer 4 is exposed.
Is formed, and an AuGe ohmic electrode 6 is formed on the lower surface of the p ⁺ type InP semiconductor substrate 1 in a pattern in which a part of the surface of the substrate 1 is exposed. On the surface of the electron emission layer 4, Cs as an alkali metal 7 is applied very thinly in order to further lower the work function.

Now, assuming that near infrared light hν enters the photoelectron emitting surface to which an appropriate bias voltage is applied from the exposed surface of the p ⁺ type InP semiconductor substrate 1, the near infrared light hν will be hν.
Penetrates the p ⁺ InP semiconductor substrate 1 and p ⁻ InGaAs
It is absorbed by the P light absorption layer 2 and excites the photoelectron e. The photoelectrons e are accelerated by the electric field formed by applying the bias voltage, and the p ⁻ InGaAsP light absorption layer 2 and the i-type InP
After passing through the interface between the intermediate layer 3 and the p ⁻ InP electron emission layer 4 and transiting from the Γ valley of the conduction band to the bottom of the L valley, it reaches the surface of the p ⁻ InP electron emission layer 4. That is, the photoelectron emission surface of this embodiment is a so-called transmissive photoelectron emission surface where incident light enters from the substrate 1 side and photoelectrons are emitted to the electron emission layer 4 side.

The characteristic point of this embodiment is that
Even if the bias voltage is low, the photoelectron e is p ^- InGaA
This is to pass through the interface between the sP light absorption layer 2 and the i-type InP intermediate layer 3 by the tunnel effect.

The surface of the p ^- InP electron emission layer 4 has a suitable C
The work function is lowered by the application of s, and the reached photoelectrons e are easily emitted to the outside from the exposed surface of the electron emission layer 4.

FIG. 2 shows an energy band diagram when the bias voltage of the photoelectron emitting surface of this embodiment is not applied. An i-type InP intermediate layer 3 is introduced between the p ⁻ InGaAsP light absorption layer 2 and the p ⁻ InP electron emission layer 4. However, in the state where the bias voltage is not applied, the photoelectrons e excited in the p ⁻ InGaAsP light absorption layer 2 cannot reach the surface of the p ⁻ InP electron emission layer 4 due to the discontinuity of the conduction band.

FIG. 3 shows an energy band diagram when a bias voltage on the photoelectron emission surface of this embodiment is applied. An internal electric field is formed by applying a bias voltage, and band bending occurs due to depletion near the surface.

P ^- InGaAsP light absorption layer 2 and p ^- In
The conduction band discontinuity between the P electron emission layers 4 is as shown in FIG. 3 due to the presence of the i-type InP intermediate layer 3. Although there is an energy barrier in the conduction band as in the conventional case, the width d of the barrier becomes narrower than in the conventional case because the InP intermediate layer 3 is i-type and therefore has a strong internal electric field. As a result, the photoelectrons e can easily pass through the energy barrier of the conduction band by the tunnel effect even if the magnitude of the bias voltage is about the same as the conventional one.

Therefore, the photoelectrons e excited in the p ^-- InGaAsP light absorption layer 2 can easily reach the surface of the p ^-- InP electron emission layer 4. Here, since the width of the energy barrier of the conduction band is narrower than in the conventional case, the bias voltage required for the photoelectrons e to pass through the barrier can be set to be much lower than in the conventional case. This suppresses the injection of holes from the Schottky electrode 5 due to the application of the bias voltage, and significantly reduces the dark current caused by the holes. Therefore, it is possible to reduce the dark current, which is the biggest drawback of this type of transition electron photoemissive surface.

Of course, in order to further reduce the interface energy barrier ΔE in the conduction band, it is effective that the i-type InP intermediate layer 3 is a graded composition layer in which the composition is gradually changed from InGaAsP to InP. Can be easily imagined. However, what is essential is that, since the intermediate layer 3 is composed of a high-resistance i-type semiconductor, photoelectrons can easily pass through the energy barrier of the conduction band by the tunnel effect, and thus the bias voltage can be set low, so that the photoelectron emission is reduced. That is, it is possible to suppress the injection of holes into the surface.

Next, FIG. 4 shows a schematic sectional view of an embodiment of the second photoelectron emitting surface according to the present invention. This photoelectron emission surface is formed on the p ⁺ type InP semiconductor substrate 1 by p ⁻ InGaAs.
P light absorption layer 2, high resistance i-type InP intermediate layer 3 thereon,
It has a III-V group compound semiconductor hetero layered structure in which an n-type InP electron emission layer 8 having a thickness of 100 Å or less is epitaxially grown thereon. Furthermore, on the electron emission layer 8,
The Al Schottky electrode 5 formed in a pattern in which at least a part of the electron emission layer 8 is exposed is formed, and p ⁺ type In
On the lower surface of the P semiconductor substrate 1, AuGe ohmic electrodes 6 are formed in layers. On the surface of the electron emission layer 8, Cs is used as an alkali metal 7 in order to further lower the work function.
Is applied very thinly.

Now, assuming that near-infrared light hν enters the photoelectron emission surface to which an appropriate bias voltage is applied from the exposed surface of the p ⁺ type InP semiconductor substrate 1, the near infrared light hν is p ⁺ type. P ^- InGaAsP through the InP semiconductor substrate 1
It is absorbed in the light absorption layer 2 and excites the photoelectrons e. The photoelectrons e are accelerated by an electric field formed by applying a bias voltage, cross the interface between the p ⁻ InGaAsP light absorption layer 2 and the i-type InP intermediate layer 3, and transit from the bottom of the Γ valley of the conduction band to the bottom of the L valley. After that, the surface of the n-type InP electron emission layer 8 is reached.

The surface of the n-type InP electron emission layer 8 has a suitable C
The work function is lowered by the application of s, and the reached photoelectrons e are easily emitted into the vacuum from the exposed surface of the n-type InP electron emission layer 8. Therefore, obviously, the photoelectron emission surface of FIG. 4 is also a so-called transmissive photoelectron emission surface.

FIG. 5 is an energy band diagram when no bias voltage is applied to the photoelectron emission surface of this embodiment.
FIG. 6 shows an energy band diagram when a bias voltage is applied.

Since the photoelectron emission surface of this embodiment also includes the intermediate layer 3 made of a high-resistance i-type semiconductor, the photoelectrons are tunneled through the energy barrier of the conduction band by the tunnel effect as in the photoelectron emission surface of FIG. Since it can easily pass therethrough and the bias voltage can be set to be much lower than in the past, it is possible to suppress the injection of holes into the photoelectron emission surface.

In addition, since the electron emission layer of the photoelectron emission surface of this embodiment is an n-type semiconductor, the strength of the internal electric field decreases near the Al Schottky electrode 5, as is apparent from FIG. There is. Therefore, the injection of holes from the Schottky electrode 5 is further suppressed. As a result, on the photoelectron emission surface of the present embodiment, it is possible to further reduce the dark current due to hole injection.

By the way, Japanese Laid-Open Patent Publication No.
The photoemissive surface shown in FIG. 12 disclosed in 2-133633 is similar to the present invention for the purpose of reducing dark current. However, this photoelectron emission surface is intended to suppress the traveling of the holes h injected from the electrode 19, and does not suppress the injection of the holes h itself. On this photoelectron emission surface, in order to reduce the dark current, an energy barrier is provided so that photoelectrons e can pass but holes h cannot pass.

In order to provide this energy barrier, FIG.
The photoabsorption layer 1 is formed on the photoelectron emission surface shown in FIG.
An additional layer 17 having an energy gap larger than those of Nos. 6 and 18 and having an appropriate film thickness is inserted between the light absorption layers 16 and 18. Therefore, this additional layer 17 is a layer having a smaller energy gap on both sides thereof, that is, the light absorption layer 1
By being sandwiched by 6 and 18, barriers are formed in the conduction band and the valence band. Even if the number of additional layers 17 is increased, the essential principle is the same.

By controlling the energy gap, polarity and layer thickness of the additional layer 17, the barrier thus formed blocks the travel of the holes h while ensuring the transmission of the photoelectrons e, so that the holes h are accelerated. It is possible to suppress the electrons generated by the collisional ionization due to, and reduce the dark current caused by the hole injection.

On the other hand, although the present invention has the same purpose of reducing the dark current, it suppresses the injection of the holes h, which are the origin of the dark current, and therefore, the i-type intermediate with high resistance is used. The layer 3 is inserted between the light absorption layer 2 and the electron emission layer 4 to cause electric field concentration at the hetero interface, thereby lowering the required bias voltage. In addition, the electron emission layer 4
Is an n-type thin film to reduce the internal electric field strength in the vicinity of the Schottky electrode 5 and suppress the injection of holes h. Therefore, according to the photoelectron emission surface of the present invention, it is not necessary to form a barrier of the valence band, and it is not necessary to sandwich the intermediate layer 3 between layers having a small energy gap. As described above, the present invention and the above-mentioned JP-A-62-133633 are essentially different in operation and structure.

In this embodiment, InP / InGaAs is used.
Although the hetero-laminated structure has been described as an example, the material for the photoelectron emitting surface is not limited to this, and is described in US Pat. PAT. 3,9
Of course, it can be applied to all the materials as disclosed in 58,143. Also, the Schottky electrode 5
Alternatively, the material used for the ohmic electrode 6 is not limited to that of the embodiment, but may be made of a metal of Al, Au, Ag, Mo, W, or Ni, a silicide, or an alloy thereof. Further, it goes without saying that the alkali metal 7 is not limited to Cs. The ohmic electrode 6 in the above embodiment is composed of Au to which Ge is added so as to have ohmic characteristics. However, the Schottky electrode 5 and the ohmic electrode 6 described in the present embodiment are not particularly limited to this, and any material having an action capable of effectively forming an electric field inside the hetero-laminated structure of semiconductors may be used. Of course.

The photoelectron emission surface according to the present invention can be applied to an electron tube utilizing the external photoelectric effect. Figure 7
FIG. 9 is a side sectional view of an example in which the photoelectron emitting surface 30 of FIG. 1 or 4 is applied to a head-on type photomultiplier tube. The structure of the photoelectron emitting surface 30 is the same as that shown in FIG. 1 or FIG.

Light hν is incident on the photoelectron emission surface 30 through the incident window 13, and photoelectrons e are emitted in the direction of the arrow opposite to the incident surface. The emitted photoelectrons e are the first dynode 1
0, and the number of 2 to 3 times the number of incident photoelectrons e.
Secondary electrons are emitted. The secondary electrons further enter the second dynode 11 and similarly emit 2-3 times more secondary electrons. By repeating this, the anode 12 finally detects as a photocurrent of about 10 ⁶ times the photoelectrons e emitted from the photoelectron emitting surface 30, and very highly sensitive photodetection becomes possible.

By the way, if the dark current on the photoelectron emission surface 30 is large at this time, the electrons generated by these dark currents are also multiplied and detected at the anode 12 in a mixed manner with the signal, resulting in S / N will be reduced. Therefore, in such a photomultiplier tube, a large dark current on the photoelectron emission surface 30 is a fatal defect as a photodetector.

The photoelectron emission surface 30 of FIG. 1 or FIG. 4 used in this embodiment has the dark current significantly reduced as compared with the conventional one, as described above, and thus the photoelectron enhancement surface of this embodiment is increased. The double tube has the excellent characteristics of high sensitivity and low noise.

FIG. 8 shows the photoelectron emitting surface 3 of FIG. 1 or 4.
It is a sectional side view of an example when 0 is applied to a near type image intensifying tube. Also here, the structure of the photoelectron emitting surface 30 is omitted because it is similar to that of FIG. 1 or FIG.

Light incident through the incident window 13 is absorbed by the photoelectron emission surface 30, excites photoelectrons, and is emitted into a vacuum. The emitted photoelectrons e enter the microchannel plate 14 installed facing the photoelectron emission surface 30. The microchannel plate 14 is composed of a secondary electron multiplying part having a large number of small holes with a diameter of about 10 μm, and the photoelectrons incident on the small holes are multiplied by about 10 ⁶ times, and further exit to the exit of the microchannel plate 14. The fluorescent substance 15 installed facing each other emits light.

Therefore, since the phosphor 15 at the position corresponding to the incident position on the photoelectron emitting surface 30 emits light, it is possible to detect the two-dimensional position of weak light. In this case as well, the dark current on the photoelectron emission surface 30 will be
Since it is multiplied by, it becomes noise and becomes a factor that deteriorates the image quality. Since the dark current is greatly reduced on the photoelectron emission surface of FIG. 1 or FIG. 4 used in this embodiment, the image intensifier tube of this embodiment to which this is applied has high sensitivity and high image quality. The two-dimensional position can be detected.

The photoelectron emitting surface according to the present invention can be applied to electron tubes other than the above, and can be used as a photoelectric target for all electron tubes utilizing the external photoelectric effect such as a streak tube.

[0053]

As described above, in the photoelectron emission surface according to the present invention, since the high resistance i-type intermediate layer is present between the light absorption layer and the electron emission layer, the strong internal portion is formed in the discontinuity portion of the conduction band. Since an electric field is generated and the photoelectrons can pass through the energy barrier due to the tunnel effect, it becomes possible to emit the photoelectrons with a bias voltage lower than the conventional one. Therefore, it is possible to significantly reduce the dark current due to the application of the bias voltage.

Furthermore, the electron emission layer has a thickness of 100.
By providing the n-type layer of Å or less, the injection of holes from the electrode in contact with the electron emission layer can be further suppressed, and thus the dark current can be further reduced.

As a result, by using the photoelectron emission surface according to the present invention, it is possible to realize a highly sensitive and low noise electron tube in which the dark current from the photoelectron emission surface is significantly reduced as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of a photoelectron emitting surface according to the present invention.

FIG. 2 is an energy band diagram when a bias voltage on the photoelectron emission surface of FIG. 1 is not applied.

3 is an energy band diagram when a bias voltage is applied to the photoelectron emission surface of FIG.

FIG. 4 is a schematic cross-sectional view of an embodiment of a second photoelectron emission surface according to the present invention.

5 is an energy band diagram when a bias voltage on the photoelectron emission surface of FIG. 4 is not applied.

6 is an energy band diagram when a bias voltage is applied to the photoelectron emission surface of FIG.

FIG. 7 is a side sectional view of an embodiment in which the photoelectron emission surface according to the present invention is applied to a head-on type photomultiplier tube.

FIG. 8 is a side sectional view of an example in which the photoelectron emission surface according to the present invention is applied to an image intensifying tube.

FIG. 9 is a schematic cross-sectional view of a conventional transition electron type photoelectron emission surface.

FIG. 10 is an energy band diagram when a bias voltage on the photoelectron emission surface of FIG. 9 is not applied.

11 is an energy band diagram when a bias voltage is applied to the photoelectron emission surface of FIG.

FIG. 12 is a schematic cross-sectional view of a photoelectron emission surface on which a thin film additional layer is formed and an energy band diagram when a bias voltage is applied to the photoelectron emission surface.

[Explanation of symbols]

1 ... p ⁺ type semiconductor substrate, 2 ... p ⁻ type semiconductor absorption layer, 3 ...
i-type semiconductor intermediate layer, 4 ... P ^- semiconductor electron emission layer, 5 ... Schottky electrode, 6 ... Ohmic electrode, 7 ... Alkali metal, 8 ... N-type semiconductor emission layer, 9 ... Glass side tube, 10 ... First diode, 11 ... 2nd dynode, 12 ... Anode, 1
3 ... Incident window, 14 ... Micro channel plate, 15
... Phosphor, 16, 18 ... p ⁺ type light absorption layer, 17 ... additional layer, 19 ... electrode, 20 ... emission layer, 21 ... window layer, 30 ... photoelectron emission surface.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // H01L 31/10

Claims (5)

[Claims] 1. A photoabsorption layer having a small energy gap formed on a substrate at a photoelectron emission surface that has a hetero-stack structure of a III-V group compound semiconductor and that absorbs incident light to excite photoelectrons. An i-type intermediate layer laminated on the upper surface of the light absorbing layer, having a larger energy gap than the light absorbing layer and having a high resistance; an electron emission layer laminated on the upper surface of the i type intermediate layer; One electrode and a second electrode in contact with the electron emission layer, wherein the incident light enters from the substrate side and the photoelectrons are emitted to the electron emission layer side. . 2. The photoelectron emitting surface according to claim 1, wherein the electron emitting layer is an n-type layer having a thickness of 100 Å or less. 3. The first electrode in contact with the substrate is formed in a pattern in which at least a part of the surface of the substrate is exposed,
The second electrode in contact with the electron emission layer is formed in a pattern in which at least a part of the surface of the electron emission layer is exposed, the incident light enters from the exposed surface of the substrate, and the photoelectrons expose the electron emission layer. The photoelectron emission surface according to claim 1, wherein the photoelectron emission surface is emitted from the surface. 4. The photoelectron according to claim 3, wherein the second electrode in contact with the electron emission layer is made of a metal of Al, Au, Ag, Mo, Ni or W, a silicide, or an alloy thereof. Emission surface. 5. An electron tube comprising the photoelectron emitting surface according to claim 1.